Motor-driven medical instruments that include electrically-, hydraulically-, or pneumatically-driven motor systems are increasingly employed in various medical fields, such as orthopedics, arthroscopy, neurosurgery and spinal surgery. All of these indications have in common that at the instrument tip of the respective instrument a tool such as a drill, milling cutter or the like is received which is driven by a motor system connected thereto or integral therewith. In order to drive the respective tool in accordance with the current conditions, the respective motor system must be adapted to be optimally controlled by a user.
In particular, in the case of surgical instruments, it is necessary to adapt or vary the operating mode of the tool, i.e. for instance a speed and/or a torque to be maximally applied in accordance with the current state of an operative procedure under precise and stable control.
DE 10 262 088 B4 shows a surgical motor system which is composed of a control device and a foot control associated therewith. A motor connecting cable is connected via a respective coupling member at its one end to the control device and at its other end to a drive or a motor unit by which a tool is adapted to be driven. Via a hand piece coupling different handpieces are mechanically coupled to the motor unit according to requirements. The motor unit then transmits an output signal (drive power) by which the tool provided at a distal end of the hand piece is operated to the control device in response to a request made to the foot control by the user.
It has turned out, however, that a partly required fine control of the motor control system by means of the foot control is not possible already for ergonomic reasons. Furthermore it is fatiguing to the foot when the latter has to remain in a particular position not resting on a plain support over a quite long period of time.
To permit a more sensitive and thus more convenient operation of a motor control system of this type, a manual control has been suggested as a control device by the afore-mentioned document, as well as by the product catalogue of the present applicant, Aesculap “Aesculap Power Systems 2008”. The manual control comprises an operating element arranged at the end piece of a motor connecting cable for setting a control signal for operating a motor unit connected to the motor connecting cable which is communicated via the motor connecting cable to a control device and can be operated by the operator when guiding a handpiece coupled to the motor unit. The operating element in the form of an operating lever extends in longitudinal direction along the motor unit in the direction of the distal instrument tip and in the handle area of the hand piece projects radially outwardly therefrom. The operating lever is pivoted with respect to the handpiece and the gripping surface formed at the same for adjusting the motor output power. Accordingly, the operator controls the motor unit by gripping the handpiece and putting a finger, preferably the index finger, onto the lever and pressing the same down in the direction of the gripping piece according to the desired operating mode opposed to a resetting force triggered by a biasing spring.
As the index finger rests on the lever and is utilized for setting the desired operating point of the motor unit, this embodiment has the drawback that in all intermediate positions of the operating lever the handpiece is not held by three but now by merely two fingers while the third one, viz. the index finger, must be held substantially freely above the gripping piece for actuating the operating element. Thus the handpiece rests in the hand in an unstable manner.
Moreover, the handpiece cannot be guided precisely by being clamped between two fingers only, as it is usually known from guiding a pencil during a writing operation. Especially when the pressure onto the tool is increased, which usually would have to be realized almost exclusively by the index finger, the drawback occurs that the fingers laterally gripping the handpiece, viz. the thumb and the middle finger, have to apply the entire force, i.e. the tool contact force, which fatigues the operator's hand already after a short period of time. Moreover, in this case there is a risk that the handpiece can slip away between the two gripping fingers (thumb and middle finger).
The neighboring state of the art can also be inferred from the documents DE 11 35 126 A, US 2009/0240272A1, US 2010/0168723A1, EP 1 629 782 B1 and JP 60 083 610.
Furthermore, in the afore-described manual control it has turned out to be a drawback that the finger actuating the operating lever (index finger) cannot permanently rest for each intermediate position but even has to work against the resetting force of the operating lever during the entire use so as to hold the operating lever at a particular position. This results in the fact that the operating finger for the operating lever fatigues, whereby it becomes increasingly difficult for the operating person to maintain a constant operating condition of the motor unit in the long run.